COLUMBUS, Ohio — The state's top elections official said Monday he accidentally invested in a company that makes voting machines.

Secretary of State Kenneth Blackwell, who is seeking the Republican nomination for governor, said he discovered the shares for Diebold Inc. while preparing a required filing for the Ohio Ethics Commission.

"While I was unaware of this stock in my portfolio, its mere presence may be viewed as a conflict and is therefore not acceptable," he said in a letter included in his filing.

Blackwell said his investments are directed by an accountant and financial adviser without his knowledge or help, "similar to a blind trust."

He said a manager of his investments account at Credit Suisse First Boston bought 178 shares of Diebold stock at $53.67 per share in January 2005. Blackwell said the manager did not follow instructions to avoid such investments.

He said 95 shares were later sold at a loss but he still held 83 shares until discovering them and liquidating them Monday, also at a loss.

The state negotiated a deal with Diebold last year for $2,700 per touch-screen machine. In a statement given in May as part of a lawsuit, Judith Grady, who oversees the secretary of state's compliance with the 2002 federal voting act, said Blackwell was not involved with price negotiations.

What had been a mundane political duty took on new meaning last year after Gov. Bob Taft's failure to report several golf outings led to his no contest plea to ethics violations. He was fined the maximum $4,000.

Bob Paduchik, a spokesman for Attorney General Jim Petro, Blackwell's rival in the GOP primary, called for further investigation.

Democrats weren't buying Blackwell's explanation.

"If he can't manage to know what's in his checkbook, why would the people of Ohio want to trust this man with the state's checkbook?" said Brian Rothenberg, spokesman for the Ohio Democratic Party.